Suppose that atomic masses were based on the assignment of a mass of 12.000 g to 1 mol of carbon, rather than 1 mol of 12C. What would the atomic mass of oxygen be? (The atomic masses of carbon and oxygen, based on the assignment of 12.000 g to 1 mol of 12C, are 12.011 amu and 15.9994 amu, respectively.)

Verified step by step guidance

Understand that the current atomic mass unit (amu) is based on assigning exactly 12 amu to one mole of 12C atoms.

Recognize that the problem asks us to consider a hypothetical situation where 1 mole of carbon atoms (not just 12C) is assigned a mass of 12.000 g.

Calculate the average atomic mass of carbon based on its isotopic composition, which is currently 12.011 amu.

Determine the ratio of the hypothetical atomic mass of carbon (12.000 g/mol) to the current atomic mass (12.011 amu/mol).

Apply this ratio to the current atomic mass of oxygen (15.9994 amu) to find its new atomic mass under the hypothetical system.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Atomic Mass Unit (amu)

The atomic mass unit (amu) is a standard unit of mass that quantifies mass on an atomic or molecular scale. It is defined as one twelfth of the mass of a carbon-12 atom, which is approximately 1.66 x 10^-27 kg. This unit allows chemists to express the mass of atoms and molecules in a more manageable way, facilitating comparisons between different elements.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is numerically equivalent to the atomic or molecular mass expressed in amu. Understanding molar mass is crucial for converting between the mass of a substance and the number of moles, which is essential for stoichiometric calculations in chemical reactions.

Relative Atomic Mass

Relative atomic mass is a dimensionless quantity that represents the average mass of an atom of an element compared to one twelfth of the mass of a carbon-12 atom. It takes into account the isotopic composition of the element and is used to determine the atomic mass of elements in the periodic table. Changes in the reference standard, such as assigning a different mass to carbon, would directly affect the calculated relative atomic masses of other elements, like oxygen.

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Atomic Mass

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A penny has a thickness of approximately 1.0 mm. If you stacked Avogadro's number of pennies one on top of the other on Earth's surface, how far would the stack extend (in km)? [For comparison, the sun is about 150 million km from Earth and the nearest star (Proxima Centauri) is about 40 trillion km from Earth.]

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Textbook Question

Consider the stack of pennies in the previous problem. How much money (in dollars) would this represent? If this money were equally distributed among the world's population of 7.0 billion people, how much would each person receive? Would each person be a millionaire? A billionaire? A trillionaire?

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Textbook Question

A pure copper sphere has a radius of 0.935 in. How many copper atoms does it contain? [The volume of a sphere is (4/3)πr³ and the density of copper is 8.96 g/cm³.]

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Open Question

What is the radius (in cm) of a pure copper sphere that contains 1.14 * 10^24 copper atoms? [The volume of a sphere is (4/3)πr^3 and the density of copper is 8.96 g/cm^3.]